Two studies of this series were completed this year: One investigated average evoked response (AER) and kinesthetic figural aftereffect (KFA) in a schizophrenic population and the other investigated monoamine oxidase activity and psychological characteristics in a normal population. The results of the first study 1) attest to the reliability and generalizability of the concept of stimulus intensity control, 2) replicate earlier findings linking augmenting to paranoid symptomatology and contrast effects to expansive symptomatology, 3) suggest that the reduction of the perceived intensity of stimuli may function to protect the individual from being inundated by stimuli. The results of the second study indicate that low MAO activity is related to stimulus seeking, high ego strength and positive affect, characteristics which are quite congruent with the mania associated with bipolar illness but difficult to reconcile with the clinical picture of schizophrenia.